Mediterranean origin and Miocene–Holocene Old World diversification of meadow fescues and ryegrasses (Festuca subgenus Schedonorus and Lolium)
The biogeography of the grass genera Festuca (subgenus Schedonorus) and Lolium, which form one of the world main forage groups, is here reconstructed for the first time using nuclear and plastid DNA data. We aimed to test previous hypotheses on the origin of the group ancestor and on the Holocene versus pre-Holocene dispersals of the most recent fodder grasses.
The Mediterranean Basin and neighbouring regions: North Africa, Southwest Asia, East and West Africa, and Eurasia.
Sampling included nearly all representatives from the native Old World distribution of this group. We used maximum parsimony, maximum likelihood and Bayesian inference methods to reconstruct phylogenetic relationships. Divergence times were estimated with a Bayesian relaxed clock and secondary calibrations derived from a fossil-dated phylogeny of grasses. Biogeographical scenarios were reconstructed with Bayesian-averaged dispersal–vicariance analysis (Bayes-DIVA) and dispersal–extinction–cladogenesis (DEC), using a stratified palaeogeographical model spanning the last 12 million years.
Meadow fescue (Festuca pratensis) originated in Eurosiberia, Southwest Asia, 2 million years ago (Ma), whereas ryegrasses (Lolium) first diversified in the eastern Mediterranean region around 4.1 Ma, splitting into two autogamous versus allogamous lineages, with Macaronesian Lolium embedded within the latter. An alternative scenario suggests, however, an early split of the Macaronesian ryegrasses. Our results support the hybrid origin of the tall fescue (Festuca arundinacea).
The ancestor of the fescues and ryegrasses originated in the western Mediterranean in the mid-Miocene. The sister relationship of the tropical African Festuca simensis to Lolium is a novel finding, suggesting a dispersal of the ancestor of the ryegrasses from Asia to East Africa in the early Pliocene. Our reconstruction rejects the hypothesis of a single Neolithic human-mediated dispersal of Lolium species from eastern to western Mediterranean areas, suggesting instead a pre-agricultural distribution of Lolium ancestors along the Mediterranean Basin since the Pliocene.